Normal Faulting at Continental Rifts and Passive Margins: Implications for Tectonic and Sedimentary Evolution

Abstract

I analyze fault geometry and fault displacement to understand the evolution of two continental rifts and two passive margins because faults in sedimentary basins are good strain markers that record past tectonic and sedimentary processes. In the Corinth Rift, I incorporate fault heaves and dips into the flexural cantilever model of continental extension to constrain the flexural strength of the lithosphere and its control on flexural footwall uplift and hanging wall subsidence. Results show that a simple shear/pure shear mechanism of deformation by planar faults, in a lithosphere with an effective elastic thickness (Te) of 10 km can reproduce the observed flexural footwall uplift, hanging wall subsidence and basin geometry in the Gulf of Corinth. In addition, model results suggest that inherited N-S topographic gradient from the Hellenide fold and thrust belt affects the evolved rift architecture in the eastern part. I analyze the plan view geometry of faults, pre-rift fabrics and magnetic anomalies to study the evolution of rifts at the boundary between juxtaposed terranes with pre-rift fabrics of contrasting orientation, by comparing the Luama and Corinth Rifts. Results suggest that the terrane boundaries and fabrics that are well oriented to the regional extension direction likely localized both rifts and that within each terrane, changes in rock type create sufficient mechanical contrast to cause rift bifurcation. Lastly, I use fault throw history to examine the relationship among tectonics, climate and sedimentation in the Gulf of Mexico and the Congo Margin, two salt-bearing passive margins. Results show that at passive margins with a mobile substrate, faults can record changes in sedimentation driven by tectonic and climatic forcing. Fault throw estimates can be used to infer missing volumes of sediment and past tectonic and climatic events, because fault offsets can be preserved despite partial erosion.